Occupied by 15 destitute families, the apartment block in the northeastern town of Salt has become a symbol of the fight against evictions brought on by Spain's housing crash.
"The eviction has been suspended," Perez said, after learning that the European Court of Justice had postponed until October 29th their order to leave, while it studies the case.
"This is the best thing that has ever happened to me in my life," added Perez, a 51-year-old immigrant from Chile.
Unable to work because she is partially sighted, she lost her home in 2010 because she could not meet the mortgage payments.
Activists from PAH, a grass-roots group set up in 2009 to fight the tide of evictions across Spain, in March occupied the building which had laid empty for three years.
Perez, who is divorced, moved in shortly afterwards with her 18-year-old daughter and her two grandchildren, aged 11 and 8.
"I had no alternative but to come here," said Perez, whose only income is a monthly disability pension of €350 ($475).
In total 43 people, including 21 minors, live in the building in a residential neighbourhood of Salt, about 80 kilometres (50 miles) north of Barcelona.
Residents share food, grow vegetables and raise chickens in the yard and the children help each other with homework.
Hundreds of activists, many wearing green t-shirts with the slogan "Stop Evictions", spent the night at the building in sleeping bags, ready to prevent residents from being turfed out by police on Wednesday.
"We came to help. We ourselves are going to be evicted and maybe later on we will need their help," said Johanan Marin, a jobless 28-year-old who came from the nearby town of Badia and spent the night in the garage with his girlfriend.
The building is in the hands of Sareb, Spain's 'bad bank', set up to pool the financial industry's toxic assets as part of a European Union-financed rescue for Spain's banking sector.
Sareb took over the building from Marenostrum, one of several Spanish banks laden with bad property assets and absorbed in the restructuring.
A Spanish court ordered that the residents of the building be evicted on Wednesday at Sareb's request. The families, backed by PAH, appealed the decision to the European Court of Justice in Strasbourg.
About 700 people live in buildings occupied by the PAH across Spain. It says it has blocked over 800 evictions by turning up in crowds and sitting on evictees' doorsteps when the bailiffs and police arrive.
The group has won widespread sympathy in Spain, where tens of thousands of people have received eviction orders.
The collapse of a property boom in 2008 and subsequent recession have driven Spain's unemployment rate over 26 percent, leaving many unable to pay mortgages on houses that have lost much of their value.
"We are 15 families but deep down we are one family. The doors are always open and we help each other out," said Bouchra Zannouti, a Moroccan woman who is six months pregnant and living in the building with her unemployed husband and their seven-year-old son.
"In the other buildings where I have lived, I did not know my neighbours. It's different here. I am very comfortable," added 15-year-old Jonathan Llamas who lives there with his mother and his elder brother.
The residents of the building erupted into cheers and hugged each other on Wednesday when they were told that the European Court of Justice had temporarily blocked their eviction.
"This measure opens a legal path to correct the judicial indecency of the Spanish courts," said a lawyer acting for the families, Manel Benet.