MATCH result, pattern$, haystack$

MATCH result, pattern$, haystack$, var1$, var2$, ...

Evaluates a POSIX ERE (extended regular expression) against a string.

In the first form, stores 1 for a match or 0 for no match into result.
In the second form, also assigns text captured by parenthesised sub-expressions to additional string variables (var1$, var2$, …).

Remarks: Matching is ASCII-only (no locale or Unicode).; All regular expressions follow POSIX ERE syntax.

Forms

Boolean match

MATCH result, pattern$, haystack$

result must be an integer variable.
pattern$ and haystack$ are strings.
Returns 1 for a match, 0 for no match.

Match with captures

MATCH result, pattern$, haystack$, cap1$, cap2$, ...

Each parenthesised group in pattern$ (e.g. (abc)) is captured and copied into successive string variables.
Missing or non-participating groups yield "".
If the pattern contains fewer capture groups than variables, the extras receive empty strings.

Examples

Simple match

MATCH R, "HELLO", "HELLO WORLD"

IF R THEN PRINT "Found"

Anchors

MATCH R, "^START", "START HERE"
PRINT R          ' 1
 
MATCH R, "END$", "THE END"
PRINT R          ' 1

Alternation and character classes

MATCH R, "CAT|DOG", "HOTDOG"
PRINT R          ' 1
 
MATCH R, "[A-Z][a-z]+", "Title"
PRINT R          ' 1

Capturing sub-expressions

MATCH R, "([A-Za-z]+),([A-Za-z]+)", "Hello,World", FIRST$, SECOND$

PRINT R, FIRST$, SECOND$ ' 1 Hello World

No match clears captures

MATCH R, "(\d+)", "No digits here", NUM$

PRINT R, NUM$ ' 0 ""

Invalid pattern handling

ON ERROR PROCbad
MATCH R, "(?i)HELLO", "hello"   ' invalid: (?i) not supported
PRINT "this line is not reached"
END
 
DEF PROCbad
PRINT "Regex error!"
END

Supported syntax (POSIX ERE subset)

Feature	Example	Description
Literals	ABC	exact characters
Any char	.	matches any single character
Quantifiers	* + ?	greedy repetition
Character classes	[abc], [A-Z], [^0-9]	set, range, negation
Alternation	A \ilinebr </td> <td class="markdownTableBodyNone"> B	match A or B
Anchors	^, $	start / end of string
Capturing groups	(ABC)	capture substring

Not supported

Backreferences \1, \2, …
Inline flags (?i) etc.
PCRE-style escapes (\d, \w, lookaround, …)
Multiline mode (^ and $ match string boundaries only)

Notes

Matching is case-sensitive. To simulate case-insensitive matching, normalise both strings or use explicit character classes.
With captures, co-operative execution is disabled - the operation completes immediately.
Without captures, matching runs co-operatively across idle ticks for long inputs.
If the pattern is invalid, the engine reports a descriptive message. Without an error handler, the program terminates; with ON ERROR PROCname, control transfers to the handler.
Capture results are always independent copies; modifying the original string has no effect on captured values.