F1 F2 F3 F4 Aa$.c$A..,.$,.,$.^~.
F1 F2 F3 F4 one^~.two.a$threeA$four.five$six
F1 F2 F3 F4 a$,b~c.d^efg
F1 F2 F3 F4 abc
F1 F2 F3 F4 ,,,,
F1 F2 F3 F4 789790

BEGIN {
    myRE = "(\\^~\\.)|(A\\$)|(\\.\\$)|[\\.\\$]";
    myChar = "[a-zA-Z][\\$\\~\\^]?";
    myFill = "[\\.\\,]";
    m = "^~. .$ . A$ A";
    acnt = split(m, astr, " ");
}
{
    print $0;
    str = $5;
    print str;
    chars = gsub(myChar, "+", str);
    print "/" str "/, found " chars;
        fills = gsub(myFill, "x", str);
    print "/" str "/, found " fills;
    if (chars + fills) {
        printf("freq = %.1f%%\n", fills * 100.0 / (fills + chars));
    } else {
        print "freq = undef";
    }
}

F1 F2 F3 F4 Aa$.c$A..,.$,.,$.^~.
Aa$.c$A..,.$,.,$.^~.
/++.++..,.$,.,$.^~./, found 4
/++x++xxxx$xxx$x^~x/, found 10
freq = 71.4%
F1 F2 F3 F4 one^~.two.a$threeA$four.five$six
one^~.two.a$threeA$four.five$six
/+++~.+++.+++++++++++.+++++++/, found 24
/+++~x+++x+++++++++++x+++++++/, found 3
freq = 11.1%
F1 F2 F3 F4 a$,b~c.d^efg
a$,b~c.d^efg
/+,++.++++/, found 7
/+x++x++++/, found 2
freq = 22.2%
F1 F2 F3 F4 abc
abc
/+++/, found 3
/+++/, found 0
freq = 0.0%
F1 F2 F3 F4 ,,,,
,,,,
/,,,,/, found 0
/xxxx/, found 4
freq = 100.0%
F1 F2 F3 F4 789790
789790
/789790/, found 0
/789790/, found 0
freq = undef


//, found 0
//, found 0
freq = undef