This

my @value;

##to get the headers of the excel file;
for my $row ( 0 .. 0 ) { 
    @value = map {
        my $cell = $worksheet->get_cell($row, $_);
        $cell ? $cell->value() : '';
    } @required_col;
}
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can be simplified to just

##to get the headers of the excel file;
my @value = map {
    my $cell = $worksheet->get_cell(0, $_);
    $cell ? $cell->value() : '';
} @required_col;
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And since you're modifying the arrays passed to your subroutine, it looks like you just need to dereference them so that you make a copy.

sub changeformat {
    my ($header,$data) = @_;
    my @header = @$header;
    my @data = @$data;
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Then only perform your operations on the new @header and @data arrays and not on $header or $data.