There are modules on CPAN for reading such files (for example Text::CSV), and there are lots of modules for producing XML.

You'll just have to put them together in a small script to do what you want.

You don't tell us what XML schema you intend to output, nor do you show any code you have attempted to write yourself.

My approach would be:

#!perl -wle

while (<>) {
    s!^!<row><value>!;
    s!\t!</value><value>!g;
    s!$!</value></row>!;
    print;
};
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If you need more structure in your XML, you will have to tell us what structure.

You would also need to escape & and < in the text, and make sure you get the encoding right.

Your data currently appears to be close to YAML format, so if you did convert it to YAML, you could do something like this:

use strict;
use warnings;
use YAML;

my $stuff = <<YAML;
---
ABC:
 DEF:
  - GHI
YAML

my $perl_structure = Load $stuff;

printit ($perl_structure);

sub printit{
  my $this = shift;
  if (ref $this eq "" ){
     print $this;
     return;
  }
  if (ref $this eq "ARRAY"){
     print "<value>";
       printit ($_) for @$this;
     print "</value>\n";
     return;
  }
  #print "Got " . ref ($this) . "\n";
  for my $k (keys %$this){
     print "<$k>\n";
     printit($_) for $this->{$k};
     print "</$k>\n";
  }
}
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<ABC>
<DEF>
<value>GHI</value>
</DEF>
</ABC>
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