s2p 's#[^0-9]*\([0-9]\{3\}\)[^0-9]*\([0-9]\{3\}\)[^0-9]*\([0-9]\{4\}\)#(\1) \2-\3#'
Having no space between pattern and following word is deprecated at (eval 1) line 27.
Bareword found where operator expected at (eval 1) line 27, near "s #\D*(\d{3})\D*(\d{3})\D*(\d{4})#(${1}) ${2}-${3}#s;
  $CondReg ||= $s;
}
EOS:    if( $doPrint"
  (Might be a runaway multi-line $$ string starting on line 25)
        (Do you need to predeclare s?)
Code:
# prototypes
sub openARGV();
sub getsARGV(;\$);
sub eofARGV();
sub printQ();

# Run: the sed loop reading input and applying the script
#
sub Run(){
    my( $h, $icnt, $s, $n );
    # hack (not unbreakable :-/) to avoid // matching an empty string
    my $z = "\000"; $z =~ /$z/;
    # Initialize.
    openARGV();
    $Hold    = '';
    $CondReg = 0;
    $doPrint = $doAutoPrint;
CYCLE:
    while( getsARGV() ){
        chomp();
        $CondReg = 0;   # cleared on t
BOS:;
# s#[^0-9]*\([0-9]\{3\}\)[^0-9]*\([0-9]\{3\}\)[^0-9]*\([0-9]\{4\}\)#(\1) \2-\3#
{ $s = s #\D*(\d{3})\D*(\d{3})\D*(\d{4})#(${1}) ${2}-${3}#s;
  $CondReg ||= $s;
}
EOS:    if( $doPrint ){
            print $_, "\n";
        } else {
            $doPrint = $doAutoPrint;
        }
        printQ() if @Q;                                                                                                            }                                                                                                                     
    exit( 0 );                                                                                                                      {                                                                                                                   
# openARGV: open 1st input file                                                                                     
#                                                                                                                   
sub openARGV(){                                                                                                     
    unshift( @ARGV, '-' ) unless @ARGV;                                                                             
    my $file = shift( @ARGV );                                                                                      
    open( ARG, "<$file" )                                                                                           
    || die( "$0: can't open $file for reading ($!)\n" );
    $isEOF = 0;
}

# getsARGV: Read another input line into argument (default: $_).
#           Move on to next input file, and reset EOF flag $isEOF.
sub getsARGV(;\$){
    my $argref = @_ ? shift() : \$_; 
    while( $isEOF || ! defined( $$argref = <ARG> ) ){
        close( ARG );
        return 0 unless @ARGV;
        my $file = shift( @ARGV );
        open( ARG, "<$file" )
        || die( "$0: can't open $file for reading ($!)\n" );
        $isEOF = 0;
    }
    1;
}

# eofARGV: end-of-file test
#
sub eofARGV(){
    return @ARGV == 0 && ( $isEOF = eof( ARG ) );
}

# makeHandle: Generates another file handle for some file (given by its path)
#             to be written due to a w command or an s command's w flag.
sub makeHandle($){
    my( $path ) = @_;
    my $handle;
    if( ! exists( $wFiles{$path} ) || $wFiles{$path} eq '' ){
        $handle = $wFiles{$path} = gensym();
        if( $doOpenWrite ){
            if( ! open( $handle, ">$path" ) ){
                die( "$0: can't open $path for writing: ($!)\n" );
            }
        }
    } else {
        $handle = $wFiles{$path};
    }
    return $handle;
}

# printQ: Print queued output which is either a string or a reference
#         to a pathname.
sub printQ(){
    for my $q ( @Q ){
        if( ref( $q ) ){
            # flush open w files so that reading this file gets it all
            if( exists( $wFiles{$$q} ) && $wFiles{$$q} ne '' ){
                open( $wFiles{$$q}, ">>$$q" );
            }
            # copy file to stdout: slow, but safe
            if( open( RF, "<$$q" ) ){
                while( defined( my $line = <RF> ) ){
                    print $line;
                }
                close( RF );
            }
        } else {
            print $q;
        }
    }
    undef( @Q );
}

s2p: internal error - generated incorrect Perl code: syntax error at (eval 1) line 27, near "s #\D*(\d{3})\D*(\d{3})\D*(\d{4})#(${1}) ${2}-${3}#s;
  $CondReg ||= $s;
}
EOS:    if( $doPrint "
syntax error at (eval 1) line 29, near "} else"
syntax error at (eval 1) line 36, near ";
}"
syntax error at (eval 1) line 46, near ";
}"
Can't use global @_ in "my" at (eval 1) line 51, near "= @_ "
Global symbol "$argref" requires explicit package name at (eval 1) line 52.
syntax error at (eval 1) line 61, near ";
}"
Can't use global @_ in "my" at (eval 1) line 72, near "= @_"
syntax error at (eval 1) line 85, near ";
}"
Missing right curly or square bracket at (eval 1) line 111, at end of line
(eval 1) has too many errors.