From what I see, the only thing wrong with your regular expression is, that you don't allow for any characters between the last match and the next match. From your data, this regular expression works :

F:\>perl -ne "while (m/\G.*?x(.)(?=x)/g) { print $1; }"
axbxxcxdsxxxtx
bcxt
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An interesting boundary case is xxxx - what do you expect to be printed ? My solution prints x, as it matches xxx and is then left with x, which does not match. Conceivably, xx would also be a solution, as you could first match xxx and then move to the second x and match xxx again.

Uhm, wasn't it you last time that told me about Death to Dot Star! last time? ;-)
I had [^x]*? where you are now using .*? - so why is .*? working here but [^x]*? not? *totallypuzzled*
--
Alfie

Yours is failing because you've anchored the match to where the previous one left off (with \G) and are also preventing moving across any 'x' characters that don't fit the x(.)(?=x) pattern by using the negative character class. The \G.*?x may traverse over an 'x' if the remainder of the expression fails.

A simpler solution if you do not want to allow a "matched" 'x' to also count as a boundary 'x' is just:

$_ = 'xaxbxcxdexfxxxx';
print $1 while /x(.)(?=x)/g;  # abcfx
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If you do want to count 'matched' 'x' chars as potential boundary chars as well -- ie, 'xxxx' would produce 'xx' because there are two 'x' characters that have an 'x' on either side -- then:

$_ = 'xaxbxcxdexfxxxx';
print $1 while /(?<=x)(.)(?=x)/g;  # abcfxx
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perl -e "print \"xaxbxxxxdexfx\" =~ /x(.)(?=x)/g"
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Cheers,
Ovid

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A pure regexp solution, although I would use jeroenes solution:

$str='xjxexrxoxexnexsx';
print join '', split /x/, $str; #prints my monkname
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Cheers,

Jeroen
"We are not alone"(FZ)

The tricky bit u and nysus seem to have missed is that he would need the 'x' when he matches 'xjxoxrxgxXx' (uppercase X for clarity) and extracts 'jorgx' rather than just 'jorg'

Jorg

"Do or do not, there is no try" -- Yoda

Aha!

Let's keep trying it regex-less.

If you need just any second character, you could use substr:

my $str='xjxexrxoxexnxexsxxx';
my $idx = -1;
my $str_2nd = '';
 
$str_2nd .= substr( $str, $idx+=2, 1) while( $idx < length $str);
 
print "\n$str_2nd\n";
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You can achieve the same with split:

my $str='xjxexrxoxexnxexsxxx';
 
my @chars = split //, $str;
my @chars_2nd;

while ( scalar @chars ){
  shift @chars;
  push @chars_2nd, shift @chars;
}
 
print join '', @chars_2nd;
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Is this more like it? Just note that these solutions don't know what each other character ('x') is. It gets trickier if you allow more than one character between each delimiter 'x'.

Jeroen
"We are not alone"(FZ)

Here's a two step reg. expression that takes care of that problem:

$line = "xaxlxxxfxixex";
$line =~ s/(x(\w)x)/$2/g;
$line =~ s/x$//;
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$_ = "xaxlxfxixex";
$line =~ s/x//g;
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