$ strace -e mmap,munmap perl -e '$n=2**20; $x="x" x $n; {my $y=$x}{my $y=$x}{my $y=$x}'
...
mmap(NULL, 1052672, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fa5d43d3000
mmap(NULL, 1052672, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fa5d2ecd000
mmap(NULL, 1052672, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fa5d2dcc000
mmap(NULL, 1052672, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fa5d2ccb000
mmap(NULL, 1052672, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fa5d2bca000
munmap(0x7fa5d2bca000, 1052672)         = 0
munmap(0x7fa5d2ccb000, 1052672)         = 0
munmap(0x7fa5d2dcc000, 1052672)         = 0
munmap(0x7fa5d43d3000, 1052672)         = 0