sub create_chart {
    my ($ydata) = @_;
    Chart::Gnuplot::DataSet->new(
        xdata => \@yfix,
        ydata => $ydata,
        style => "lines",
        color => "dark-gray",
        linetype => "dash",
        width => 1,
    );
}

my $tempmin = create_chart(\@minit);
my $tempmax = create_chart(\@maxit);
[download]

If you want to change other attributes, too, you might use default values with named attributes:

sub create_chart {
    my (%args) = @_;

    die "No ydata\n" unless exists $args{ydata};
    
    Chart::Gnuplot::DataSet->new(
        xdata => \@yfix,
        style => "lines",
        color => "dark-gray",
        linetype => "dash",
        width => 1,
        %args
    );
}


my $tempmin = create_chart(ydata => \@minit);
my $tempmax = create_chart(ydata => \@maxit, color => 'red');
[download]

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
[download]