You can use the function stat for getting informations about a file:

my @info = stat($file);
my $last_access =  $info[8];
my $last_modification = $info[9];
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more information about stat(): perldoc -f stat

You can also use the file test operators for that.

# Age of file in days since modification:
-M $file
# Age of file in day since last access:
-A $file 
# Age of file in days since inode change:
-C $file
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For more information read perldoc perlop