use strict;
use warnings;

sub partition_usage {
    my $partition = shift;
    my $line = (`/bin/df -B 1024 $partition`)[-1];
    return 1024 * (split(/\s+/, $line))[2];
}

# test it:
print partition_usage('/home/'), "\n";

##</code><code>##

my @files = glob 'logfile_*.log.gz';
@files = reverse sort { -M $a <=> -M $b } @files. 

##</code><code>##

my $limit = 10 * 1024**3; # 10 GB
for my $filename (@files) {
    last if partition_usage('/var/log/') < $limit;
    unlink $filename or warn "Can't delete file '$filename': $!";
}