exec a perl command in Tcl with dollar sign

Question

I call a grep/perl command to extract a substring from a file in a tcl script. However I can't find a way to escape $ in perl script.

Here is my command:

set varA [exec grep ^library $file | perl -pe 's/.*\(\s*"*(.*?)"*\s*\).*/$1/']

tcl will report error no variable '1'. I escaped $ with {$} per some guidance, however the perl command just doesn't work after the {} escape. Any suggestion?

Answer 1

Wrap the entire argument in curly braces to prevent evaluation:

set varA [exec grep ^library $file | perl -pe {s/.*\(\s*"*(.*?)"*\s*\).*/$1/}]

Or skip the exec and just do it all in tcl:

proc fetch_file {filename} {
    set f [open $filename]
    set result ""
    while {[gets $f line] >= 0} {
        if {[string equal -length 7 library $line]} {
            lappend result [regsub {.*\(\s*"*(.*?)"*\s*\).*} $line {\1}]
        }
    }
    close $f
    return [join $result \n]
}

set varA [fetch_file $file]