Regular Expressions 101

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/
^(>|=|<|~|>=|=<)?(1000)$
/
gm
^ asserts position at start of a line
1st Capturing Group
(>|=|<|~|>=|=<)?
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
1st Alternative
>
> matches the character > with index 6210 (3E16 or 768) literally (case sensitive)
2nd Alternative
=
= matches the character = with index 6110 (3D16 or 758) literally (case sensitive)
3rd Alternative
<
< matches the character < with index 6010 (3C16 or 748) literally (case sensitive)
4th Alternative
~
~ matches the character ~ with index 12610 (7E16 or 1768) literally (case sensitive)
5th Alternative
>=
>=
matches the characters >= literally (case sensitive)
6th Alternative
=<
=<
matches the characters =< literally (case sensitive)
2nd Capturing Group
(1000)
1000
matches the characters 1000 literally (case sensitive)
$ 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