Read the perlfunc sections about "-X", "stat" and "time".

use 5.010;
use strict;

my $modified_within  = 60 * 5;           # 5 minutes
my $size_limit       = 1024 * 1024 * 2;  # 2 MB

my $file = "/some/file/name";

if ([stat $file]->[9] > time - $modified_within)
{
    if (-s $file > $size_limit) {
        say "File is recent, and over size limit";
    }
    else {
        say "File is recent, but not over size limit";
    }
}
else
{
    say "File is not recent";
}
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