In the 1980s and 1990s, its use faded as newer languages such as AWK and Perl made string manipulation by means of regular expressions fashionable.
[4][5]) The later SL5 (1977)[6] and Icon (1978) languages were designed by Griswold to combine the backtracking of SNOBOL4 pattern matching with more standard ALGOL-like structuring.
The initial SNOBOL language was created as a tool to be used by its authors to work with the symbolic manipulation of polynomials.
However the macro features of the assembler were used to define the virtual machine instructions of the SNOBOL Implementation Language, the SIL.
[8] The machine-independent language SIL arose as a generalization of string manipulation macros by Douglas McIlroy, which were used extensively in the initial SNOBOL implementation.
[9][10] SNOBOL is distinctive in format and programming style, which are radically different from contemporary procedural languages such as Fortran and ALGOL.
SNOBOL4's programmer-defined data type facility was advanced at the time—it is similar to the records of the earlier COBOL and the later Pascal programming languages.
Complex SNOBOL patterns can do things that would be impractical or impossible using the more primitive regular expressions used in most other pattern-matching languages.
It is possible to write, for example, a SNOBOL4 pattern which matches "a complete name and international postal mailing address", which is well beyond anything that is practical to even attempt using regular expressions.
SNOBOL4 pattern-matching uses a backtracking algorithm similar to that used in the logic programming language Prolog, which provides pattern-like constructs via DCGs.
He used the design as the basis of a graduate class in string processing that he taught that year at Stevens Institute of Technology (which is why it was named SITBOL).
Macro SNOBOL4 in C written by Phil Budne is a free, open source implementation, capable of running on almost any platform.
Minnesota SNOBOL4, by Viktors Berstis, the closest PC implementation to the original IBM mainframe version (even including Fortran-like FORMAT statement support) is also free.
After many years as a commercial product, in April 2009 SPITBOL was released as free software under the GNU General Public License.
According to Dave Farber,[16] he, Griswold and Polonsky "finally arrived at the name Symbolic EXpression Interpreter SEXI."
We sat and talked and drank coffee and shot rubber bands and after much too much time someone said — most likely Ralph — "We don't have a Snowball's chance in hell of finding a name".