A fix is simple, like the attached file.

The problem is as pointed out in comment #1 that this behavior is intended:

libinterp/corefcn/load-save.cc

  // Guard against things like 'save a*', which are probably mistakes...

  else if (i == argc - 1 && glob_pattern_p (argv[i]))
    print_usage ();

But I would argue that in MATLAB, save('a*') will simply save all variables to a file named "a*.mat", without a warning.

(file #39124)

In this case

> save ab*

I think we should save all variables to the file "ab*", since the document say

 -- Command:  save file
 -- Command:  save options file
 -- Command:  save options file V1 V2 ...
 -- Command:  save options file -struct STRUCT F1 F2 ...

It's the first form of this command.
The first non-option string is always a filename.

Well, yes, "ab*" is a bed name although.... or maybe make it a warning instead of error?

octave tell me "error: Invalid call to save." etc when I run

a=1; b=1;
save('a[s]')

The expected result is saving all variables into the file named "a[s]"
Problem also exist in version 3.6.2 and 3.4.3

Seems that it's relate to the wildcard patterns [ list ] match function in save().

Luckily, this works:

a=1; b=1;
save('a[s]','*')