my @outputlist = join s/(^\s+|\s+$)//g, $output;

I, too, am puzzled by what you are trying to achieve overall. But the particular statement quoted above is problematic. Because the prototype (see Prototypes in perlsub) of join is  $@

c:\@Work\Perl>perl -e "print prototype 'CORE::join'"
$@
[download]

the  s/(^\s+|\s+$)//g expression (which does a substitution on the  $_ default scalar) is evaluated in scalar context and the success or failure of the substitution (1 or empty string, respectively) | number of substitutions is returned and used as the join string (update: i.e., as the result of the EXPR in join EXPR,LIST).

c:\@Work\Perl>perl -wMstrict -MData::Dump -le
"my $output = 'something or other';
 ;;
 $_ = '   who knows what   ';
 my @outputlist = join s/(^\s+|\s+$)//g, $output;
 dd \@outputlist;
"
["something or other"]
[download]

But that doesn't matter because there is only one item in the join list, namely $output, so the result of the joining EXPR is never used.

c:\@Work\Perl>perl -wMstrict -MData::Dump -le
"my $output = 'something or other';
 ;;
 $_ = '   who knows what   ';
 my @outputlist = join 'anything at all', $output;
 dd \@outputlist;
"
["something or other"]
[download]

Update: Here's the result of an experiment showing what happens if there is more than one string to be join-ed:

c:\@Work\Perl>perl -wMstrict -MData::Dump -le
"my $output = 'something or other';
 ;;
 $_ = '   who knows what   ';
 my @outputlist = join s/(^\s+|\s+$)//g, $output, 'hoo', 'ha';
 dd \@outputlist;
 print qq{default scalar after s///: '$_'};
"
["something or other2hoo2ha"]

default scalar after s///: 'who knows what'
[download]

In any event, there will never be more than one element in the  @outputlist array.

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.