#!/usr/bin/perl -w
$ALIAS = 0;
$arg = 'ST(0)';
$var = 'self';
$pname = 'MyMod::MyFunc';
$expr = '\n    if (SvROK($arg) && SvTYPE(SvRV($arg))==SVt_PVHV)
        $var = (HV*)SvRV($arg);
    else
        Perl_croak(aTHX_ \"%s: %s is not a hash reference\",
            ${$ALIAS?\q[GvNAME(CvGV(cv))]:\qq[\"$pname\"]},
            \"$var\");\n'
;
 $str = qq/"\\n$expr;\\n"/;
$res = eval $str;
0;

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Can someone explain why this works? All of it. Its from ParseXS. I also can't find any documentation on "${" operator.

edit: changed typemap string from double to single quotes so eval works

In reply to why this works? quoted strings by patcat88

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