How about this:

#!/usr/bin/perl -wT
use strict;

my $txt = "  apple    bannana   lemon  ";
print "Before: '$txt'\n";

$txt =~ s/(^\s+)|(\s+$)//g;    # remove leading and trailing spaces;
$txt =~ s/\s+/\|/g;            # collapse multiple spaces into a singl
+e '|'

print "After:  '$txt'\n";

=output
Before: '  apple    bannana   lemon  '
After:  'apple|bannana|lemon'
[download]

-Blake