As I mentioned in the beginning: there are a lot of competitors implementing almost the same functionality. But all of their implementations don't follow my requirements -- to be simple, to be easy, to be flexible (but someone could say this is personal favor. May be...) That's why I have reinvented the wheel.

And one question has arised. What is the best namespace for the module?

Thank evevryone how was involved into this fruitful discussion. I have improved the module. Please have a look and give your feedback.

The source code in the actual state is located on github by the link https://github.com/ildar-shaimordanov/indent-pm. Here I am posting the minimized version (no POD, no more descriptions, the bare code only and some examples of use cases).

Example 1:

    use Indent( text => " ", eol => 1, level => 1 );

    my @str = qw( down stairs to hell );

    Indent::printf "@str";
    ( Indent::over, Indent::printf $_ ) for ( @str );
    Indent::reset;
    Indent::printf("there is no way");
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Example 2:

    use Indent;
    our $indent = Indent->new( text => " ", eol => 1, level => 1 );

    local $\ = "\n";
    my @str = qw( down stairs to hell );

    print($indent, "@str");
    {
        local $indent = $indent;
        ( ++$indent )->printf($_) for ( @str );
    }
    print($indent - 1, "there is no way");
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Source code:

package Indent;

use strict;
use warnings;

# ====================================================================
+=====

# Clamp a value on the edge, that is minimum. 
# So the value can't be less than this restriction.
sub _lclamp {
    my ( $min, $v ) = @_;
    $v < $min ? $min : $v;
}

# Set the valid level and evaluate the proper indentation.
sub _set_indent {
    my $p = shift;
    my $v = shift // 0;

    $p->{level} = _lclamp( 0, $p->{level} += $v );
    $p->{indent} = $p->{text} x $p->{level};
}

# Detect argument type and get the level value
sub _get_level {
    my $v = shift;
    ref $v eq __PACKAGE__ ? $v->{level} : $v;
}

# ====================================================================
+=====

sub new {
    my $class = shift;
    my %p = @_;

    my $self = {
        text => $p{text} // ( $p{tab} ? "\t" : " " x _lclamp( 1, $p{si
+ze} // 4 ) ),
        EOL => $p{eol} ? "\n" : $\,
        level => _lclamp( 0, $p{level} // 0 ),
    };

    _set_indent $self;

    bless $self, $class;
}

# ====================================================================
+=====

use overload (
    '=' => sub {
        my $self = shift;
        bless { %{ $self } }, ref $self;
    },
    '""' => sub {
        shift->{indent};
    },
    '++' => sub {
        _set_indent shift, +1;
    }, 
    '--' => sub {
        _set_indent shift, -1;
    },
    '+' => sub {
        my $self = shift;
        my $v = shift;

        my %self = %{ $self };
        _set_indent \%self, +_get_level($v);

        bless { %self }, ref $self;
    },
    '-' => sub {
        my $self = shift;
        my $v = shift;

        my %self = %{ $self };
        _set_indent \%self, -_get_level($v);

        bless { %self }, ref $self;
    },
);

# ====================================================================
+=====

sub import {
    shift;
    goto &config if @_;
}

# ====================================================================
+=====

my $indent;

sub config {
    $indent = __PACKAGE__->new(@_);
}

sub reset {
    $indent = $indent - $indent;
}

sub over {
    $indent++;
}

sub back {
    $indent--;
}

sub print {
    my $self = ref $_[0] eq __PACKAGE__ ? shift : $indent;

    local $\ = $self->{EOL};
    CORE::print $self, @_;
}

sub vprint {
    my $self = shift;

    local $\ = $self->{EOL};
    CORE::print $self, $_ for ( @_ );
}

sub printf {
    my $self = ref $_[0] eq __PACKAGE__ ? shift : $indent;

    $self->print(sprintf shift // "", @_);
};

1;

# ====================================================================
+=====

# EOF
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