input.txt
This is an example section.
And the second line has structural science.

jabb.txt
eg <tab> example
exp <tab> expand
sect <tab> section 
sci <tab> science

output.txt (required output)
This is an eg sect.
And the second line has structural sci.

##</code><code>##

use strict;
use warnings;

   open( ABB, '<', 'jabb.txt' ) or die "Couldn't open ABB.\n$!";
   open( IN, '<', 'input.txt' ) or die "Couldn't open infile.\n$!";
   open( OUT, '>', 'output.out' ) or die "Couldn't open outfile.\n$!";
   
   my @myin = <IN>;

   while(<ABB>){
      if(/(.*?)\t(.*?)\n/){
      my $abb=$1;
      my $full=$2;
      print "@myin\n";
      @myin = s/$full/$abb/g;
      }
  }
  print OUT "@myin\n";