Regular Expressions 101

^start of line

Group 1([^;]+)

Negated Character Class[^;]+

+matches at least one character outside the set below:

;the literal ; (59₁₀ / 73₈ / 3B₁₆)

Group 2(;\s*charset=[a-z0-9-]*)?

?repeats the group contents below at most once:

;the literal ; (59₁₀ / 73₈ / 3B₁₆)

\s*any whitespace character, repeated any number of times

charset=the literal text charset= (case insensitive)

Character Class[a-z0-9-]*

*matches any number of characters from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case insensitive)

0-9one character from 0 (48₁₀) to 9 (57₁₀)

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Group 3(.*)

.*any character (except for line terminators), repeated any number of times

$end of line

Global pattern flags

i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

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

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

^([^;]+)(;\s*charset=[a-z0-9-]*)?(.*)$

New

multipart/form-data; boundary=X
multipart/form-data; boundary="X"
multipart/form-data; charset=UTF-8
multipart/form-data; boundary=
multipart/form-data; foo=bar
multipart/form-data; bogus=1
multipart/form-data;boundary=X;charset=UTF-8
multipart/form-data; charset=UTF-8;   boundary=X
multipart/form-data;  boundary=X;  charset=ISO-8859-1
multipart/form-data; boundary=X; foo=bar
multipart/form-data; boundary=X; charset=UTF-8; foo=bar