An alternate approach lets command_line switches do most of the work.

C:\Users\Bill\forums\monks>type merg.pl
#!perl -F/,/an
use strict;
use warnings;
#
our @animals;
next if $F[0] eq 'NAME';
push @animals, [@F[0,1]] if $F[2] eq "herbivore\n";

END{
    our @animals;
    printf "\n%-15s %10s\n\n", 'NAME', 'LEG_LENGTH';
    printf "%-15s %4.2f\n" x scalar (@animals),
        map {@$_}
            sort {$$a[1] > $$b[1]} @animals;
}

C:\Users\Bill\forums\monks>perl merg.pl file1.txt file2.txt

NAME            LEG_LENGTH

Triceratops     0.87
Hadrosaurus     1.20
Stegosaurus     1.40
Euoplocephalus  1.60
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