You'll have to post a bit more code then, because my demo program doesn't suffer from the same problem:

#!/usr/bin/perl

my @current_sentence = qw(so we can do it again yeah yeah);

print "current_sentence element: $_\n" for (@current_sentence);
$string = "@current_sentence";

print "String Before: $string\n";
if( $string =~ /.*\bso\b.*/ ) {
   print "String After: $string\n";
}
[download]

OUTPUT

current_sentence element: so
current_sentence element: we
current_sentence element: can
current_sentence element: do
current_sentence element: it
current_sentence element: again
current_sentence element: yeah
current_sentence element: yeah
String Before: so we can do it again yeah yeah
String After: so we can do it again yeah yeah
[download]

Although I don't really like the $scalar = "@array" construct, I see nothing wrong with it. I would probably use: $scalar = join(' ',@array) instead for clarity.

-Blake