In your last code snippet I think the ... "_ear" eq substr $_, -3; is only going to look at the last three characters so the condition will never be true.

$ perl -le '
$str = q{bit_of_a_pigs_ear};
print
   q{_ear} eq substr( $str, -3 )
   ? q{Match found}
   : q{No match};
print
   q{_ear} eq substr( $str, -4 )
   ? q{Match found}
   : q{No match};'
No match
Match found
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I hope this is of interest.