おさらい

　A1⇔(1,1)、Z1⇔(26,1)、AA1⇔(27,1)、AZ1⇔(52,1)、BA1⇔(53,1)、...

セル名⇒行・列番号

# cell2cr( 'B2' ) ⇒ ( 2, 1 )
sub cell2cr {
    my( $cell, $col_offset, $row_offset ) = @_;

    my( $col_name, $row ) = $cell =~ /^([A-Z]+)(\d+)$/i;
    $col_name or die;
    $row      or die;
    my $col = 0; $col = $col * 26 + ord( $_ ) - 64 foreach split //, uc $col_name;

    return ( $col + $col_offset, $row + $row_offset ); # 1 origin
}

行・列番号⇒セル名

# cr2cell( 2, 1 ) ⇒ 'B1'
sub cr2cell { # 1 origin
    my( $col, $row, $col_offset, $row_offset ) = @_;

    $col += $col_offset; 0 < $col or die;
    $row += $row_offset; 0 < $row or die;
    my $col_name = '';
    do {
        $col--;
        $col_name = chr( 65 + $col % 26 ). $col_name;
        $col = int $col / 26;
    } while $col;

    return $col_name. $row;
}

セル名とオフセット

# _cell( 'A1', 2,1 ) ⇒ 'C2'
sub _cell {
    return cr2cell( cell2cr( @_ ));
}