use strict; use warnings; 

my $inputtext="a multi\nline\nstring\nanother line\n"; 
print $inputtext; 

my $newText = replaceText($inputtext, 'line', 'xx');
print "\n\n".$newText; 

sub replaceText{

	my($inputText, my $regex, my $replacement)= @_;
	$inputText =~ s/$regex/$replacement/g; 
	return $inputText;

}