use strict;
my $str = '$data = explode("|", $file[0]);
$xdata=explode("|", $xfile[1]);
$ydata = explode("|", $yfile[2]);
';
my $regex = qr/^(\s*?\$[^=]+= *explode.*?)\);/mp;
my $subst = '$1 ?? \'\');';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html