Regular Expressions 101

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/
^(?>.*?(\pL)(?!.*\1)){26}
/
gmi
^ asserts position at start of a line
Atomic Group
(?>.*?(\pL)(?!.*\1)){26}
Non-capturing group that discards backtracking positions once matched.
{26} matches the previous token exactly 26 times
.
matches any character (except for line terminators)
*? matches the previous token between zero and unlimited times, as few times as possible, expanding as needed (lazy)
1st Capturing Group
(\pL)
\pL matches any kind of letter from any language
Negative Lookahead
(?!.*\1)
Assert that the Regex below does not match
.
matches any character (except for line terminators)
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\1 matches the same text as most recently matched by the 1st capturing group
Global pattern flags
g modifier: global. All matches (don't return after first match)
m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)
i modifier: insensitive. Case insensitive match (ignores case of [a-zA-Z])
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
gmi

Test String

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