regex101: PCRE (Legacy) Match Workspace

Explanation

Pro

Non-Capturing Group(?:^|\s+)

1st Alternative^

^start of string

2nd Alternative\s+

\s+any whitespace character, repeated at least once

Non-Capturing Group(?:(?<mention>@)|(?<hash>#))

1st Alternative(?<mention>@)

Group mention(?<mention>@)

@the literal @ (64₁₀ / 100₈ / 40₁₆)

2nd Alternative(?<hash>#)

Group hash(?<hash>#)

#the literal # (35₁₀ / 43₈ / 23₁₆)

\w+any word character, repeated at least once

Positive Lookahead(?=\s+)

\s+any whitespace character, repeated at least once

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

Quick Reference

25 tokens

Regular Expression

(?:^|\s+)(?:(?<mention>@)|(?<hash>#))\w+(?=\s+)

New

@hello friend - @hello must be matched as a mention.
@ hello friend - here there should be no matches.
hey@hello @hello - here only the last @hello must be matched as a mention.
@hello! hi @hello #hi ##hello - here only the second @hello and #hi must be matche

Extraction

@hello friend - @hello must be matched as a mention.
@ hello friend - here there should be no matches.
hey@hello @hello - here only the last @hello must be matched as a mention.
@hello! hi @hello #hi ##hello - here only the second @hello and #hi must be matche