BEGIN {
        m = "^~. .$ . A$ A";
        acnt = split(m, astr, " ");
}
{
        print $0;
        for (i = 1; i <= acnt; ++i) {
                mtch = astr[i];
                c = split($5, a, mtch);
                print "Match " i ": " astr[i] " = " c
        }
}

Match 1: ^~. = 1
Match 2: .$ = 2
Match 3: . = 8
Match 4: A$ = 1
Match 5: A = 3

F1 F2 F3 F4 Aa$.c$A..,.$,.,$.^~.
F1 F2 F3 F4 one^~.two.$threeA$four.five$six

BEGIN {
    myRE = "(\\^~\\.)|(A\\$)|(\\.\\$)|[\\.\\$]";
    m = "^~. .$ . A$ A";
    acnt = split(m, astr, " ");
}
{
    print $0;
    c = split($5, a, myRE);
    for (i = 1; i <= c; ++i) {
        print "SPLIT " i ": " a[i]
    }
    str = $5;
    p = match(str, myRE, a);
    i = 1;
    while (p) {
        strsplit = substr(str, 1, RSTART - 1);
        strdelim = substr(str, RSTART, RLENGTH);
        if (strdelim in freq) {
            ++freq[strdelim];
        } else {
            freq[strdelim] = 1;
        }
        str = substr(str, RSTART + RLENGTH);
        print "Match " i ": /" strsplit "/ /" strdelim "/ /" str "/";
        ++i;
        p = match(str, myRE, a);
    }
    print "Match " i ": /" str "/";
}
END {
    for (x in freq) {
        xstr = "/" x "/";
        printf("%10s %3d\n", xstr, freq[x]);
    }
}

F1 F2 F3 F4 Aa$.c$A..,.$,.,$.^~.
SPLIT 1: Aa
SPLIT 2: 
SPLIT 3: c
SPLIT 4: A
SPLIT 5: 
SPLIT 6: ,
SPLIT 7: ,
SPLIT 8: ,
SPLIT 9: 
SPLIT 10: 
SPLIT 11: 
Match 1: /Aa/ /$/ /.c$A..,.$,.,$.^~./
Match 2: // /./ /c$A..,.$,.,$.^~./
Match 3: /c/ /$/ /A..,.$,.,$.^~./
Match 4: /A/ /./ /.,.$,.,$.^~./
Match 5: // /./ /,.$,.,$.^~./
Match 6: /,/ /.$/ /,.,$.^~./
Match 7: /,/ /./ /,$.^~./
Match 8: /,/ /$/ /.^~./
Match 9: // /./ /^~./
Match 10: // /^~./ //
Match 11: //
F1 F2 F3 F4 one^~.two.$threeA$four.five$six
SPLIT 1: one
SPLIT 2: two
SPLIT 3: three
SPLIT 4: four
SPLIT 5: five
SPLIT 6: six
Match 1: /one/ /^~./ /two.$threeA$four.five$six/
Match 2: /two/ /.$/ /threeA$four.five$six/
Match 3: /three/ /A$/ /four.five$six/
Match 4: /four/ /./ /five$six/
Match 5: /five/ /$/ /six/
Match 6: /six/
      /.$/   2
     /^~./   2
       /./   6
      /A$/   1
       /$/   4