Regular Expressions 101

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^\s*[\r\n]
/
img
^ asserts position at start of a line
\s
matches any whitespace character (equivalent to [\r\n\t\f\v \u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
Match a single character present in the list below
[\r\n]
\r matches a carriage return (ASCII 13)
\n matches a line-feed (newline) character (ASCII 10)
Global pattern flags
i modifier: insensitive. Case insensitive match (ignores case of [a-zA-Z])
m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)
g modifier: global. All matches (don't return after first match)
Your regular expression does not match the subject string.

Regular Expression
No Match

/
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img

Test String

Substitution

Processing...