I apologize for the confusing title, I'm in new regex territory (for me) here. I've been working my way through the excellent Mastering Regular Expressions, but I must be missing something.

I'm attempting to solve a problem wherein I'm finding a particular string in text: this string is optionally surrounded by '{' and '}'. In other words, the closing brace needs to be matched if and only if the opening brace was there.

I simplified the issue to a very minimal case in order to construct the regex, but I am getting unexpected results. Perhaps a more savvy monk than I can enlighten me as to where I've gone wrong. 

use strict;
use warnings;

for (
    'oh {hello} there',
    'oh {hello there',
    'oh hello there',
    'oh hello} there',
) {
    print '',
     ( $_ =~ /
              ([{]{0,1})  # optional opening brace
              hello       # .. followed by 'hello'
              (?(1)\})    # a closing brace iif the open brace was the
+re
             /x ? 'YEP ' : 'NOPE' ),
     " - $1\n";
}

[download]

This program outputs the following lines: 

YEP  - {
NOPE - 
NOPE - 
YEP  -

Expected / desired results are: 

YEP  - {
NOPE -
YEP  -
NOPE -

What in the world am I missing?

<–radiant.matrix–>
Ramblings and references
The Code that can be seen is not the true Code
I haven't found a problem yet that can't be solved by a well-placed trebuchet

In reply to Regex conditional match if previous match in same expression is true? by radiantmatrix

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