There is some tricky stuff with split.

#!/usr/bin/perl -w
use strict;

my $a = "124 abc78980 abc 9872345987abcbca4321";
my $variable = "abc";
my @line=split(/$variable/,$a);
print join("\n",@line),"\n";
__END__
prints:
124 
78980 
 9872345987  #interesting
bca4321      #also interesting
[download]

It would be helpful if you could provide an input string and what you expect the output to be.