Regular Expressions 101

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/
^\+{0,2}\d+(?:\b \b|\d)+$
/
gm
^ asserts position at start of a line
\+
matches the character + with index 4310 (2B16 or 538) literally (case sensitive)
{0,2} matches the previous token between 0 and 2 times, as many times as possible, giving back as needed (greedy)
\d
matches a digit (equivalent to [0-9])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
Non-capturing group
(?:\b \b|\d)+
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
1st Alternative
\b \b
\b assert position at a word boundary: (^\w|\w$|\W\w|\w\W)
matches the character with index 3210 (2016 or 408) literally (case sensitive)
\b assert position at a word boundary: (^\w|\w$|\W\w|\w\W)
2nd Alternative
\d
\d matches a digit (equivalent to [0-9])
$ asserts position at the end of a line
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