Regular Expressions 101

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/
(?i)\bword\b
/
gm
(?i)
match the remainder of the pattern with the following effective flags: gmi
i modifier: insensitive. Case insensitive match (ignores case of [a-zA-Z])
\b assert position at a word boundary: (^\w|\w$|\W\w|\w\W)
word
matches the characters word literally (case insensitive)
\b assert position at a word boundary: (^\w|\w$|\W\w|\w\W)
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)
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
gm

Test String