use warnings;
use strict;

my $f1 = '1.txt'; # set up files 1 through 3
my $f2 = '2.txt';
my $f3 = '3.txt'; 

my %ids;
my $fh;
open $fh, '<', $f2 or die;
while (<$fh>) {
    chomp;
    my ($name, $id) = split /_/;
    $ids{$name} = $id;
}
close $fh;

open my $fho, '>', $f3 or die;
open $fh, '<', $f1 or die;
while (<$fh>) {
    for my $name (keys %ids) {
        s/$name/${name}_$ids{$name}/;
    }
    print $fho $_;
}
close $fh;
close $fho;
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Welcome vcorby,

Your script isn't doing what you think! Please look at 'split'. You need to 'slurp' the file into an array or use a loop to get your first file. (untested)

      my @strings = ();
      open (my $F1, "<", $f1) || die "! open-100 $!";;  # open file 1 
      while ( my $input = <$F1> )
      {    chomp( $input ); # take off the line breaks
           $strings[$#strings] = $input;
      }
      close $F1;
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And life will be easier for you if you start using the 3 parameter 'open' from the beginning:

      open (my $F3, ">", $f3 ) || die "! open-300 $!";
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Note: I like to number my 'die's so it's quicker to find the problem. If you have a 50K line script, you'll be glad you did :-).

Regards...Ed

I can think of one quick-and-dirty solution that would work for small files but wouldn't scale up well to large ones, so I'll assume the files might be large. First, turn file2 into a hash, with the first part of each line as the key and the second part as the value. Then, loop through the lines of file1, check to see if each "word" is in the hash, and append its value to it if it is. Something like this:

#!/usr/bin/env perl
use 5.010; use warnings; use strict;

my %h;
open my $fd2, '<', 'file2' or die $!;
while (<$fd2>){
    chomp;
    my($k, $v) = split /_/;
    $h{$k} = $v;
}

open my $fd1, '<', 'file1' or die $!;
while (<$fd1>){
    s/(\w+)/$h{$1}?"${1}_$h{$1}":$1/ge;
    print;
}
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Oh, and here's the quick and dirty solution, which reads all of file1 into memory:

perl -e '$f1=`cat file1`;open $f2,"<","file2";while(<$f2>){chomp;($k,$
+v)=split "_";$f1=~s/$k/${k}_$v/g;}print $f1;'
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Seeing open FHwithout matching close FHbothers me. The behavior might be correct -- heck, for all I know, Perl might even by design do the right thing -- but it jangles my OCD nerve.

    open (FH, $f1) || die;  # open file 1 in a file handle
    chomp(@strings = <FH>); # take off the line breaks
--> close FH;

    open (FH, $f2) || die; # open file 2 in a file handle
    $text = join '', <FH>; # joins files 1 and 2? - I don't think I wa
+nt to do this...
--> close FH;
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Yes, a close is the best way.
However in this situation, a new OPEN for that same filehandle will cause a "close" before the next OPEN happens.
So basically this "works".

I love Perl.

Similar to the above posts but with very slight difference.

use strict;
use warnings;
use Data::Dumper;

open ( my $fh2, '<', 'file2.txt') or die ("cannot open file1: $!");
my %test;
while(my $line = <$fh2> ){
    chomp $line;
    my( $part1, $part2) = split(/_/, $line);
       $test{$part1} = $part2;
   }
close $fh2;
open ( my $fh1, '<', 'file1.txt') or die ( "Cannot open the file2: $!"
+);
my @file1;
while (my $line = <$fh1>) {
    chomp $line;
    push @file1, split /,/, $line;
}
close $fh1;
open(my $wh, '>', 'file3.txt') or die ( "cannot open file2 to write: $
+!");

for my $file1 (@file1) {
    if (exists $test{$file1}) {
        print $wh join("_", ($file1, $test{$file1}."\n" ));
    }
}
    
close $wh;
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