I need a regex, a regex is what I need
Well I need a regex, a regex is is what I need
And I said I need regex, regex; a regex is what I need
And if I share with you my story would you share your regex with me

-- Aloe Blacc - I need a dollar

Like said above, it sounds like you want the /s modifier.

use strict;
use warnings;

my $foo = "blabla foo \n yadayada \n bar bla bla";
print "\n<--\n$foo\n-->\n";

$foo =~ s/foo.+bar//s;
print "\n<--\n$foo\n-->\n";
__END__
Output:

<--
blabla foo 
 yadayada 
 bar bla bla
-->

<--
blabla  bla bla
-->
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