How to use input in newcommand?

I want to implement an insert text wrapped in some additional tags using the input command. But I get LaTeX Error: There's no line here to end.. How to do it properly? Here is my minimal reproducible example:

style.cls – defines commands

NeedsTeXFormat{LaTeX2e}
ProvidesClass{style}[Some class]
LoadClass{report}


newcommand{task}[1]{  % Command for defining the text that I want to insert
  gdef@task{#1}
}

newcommand{typeTask}{  % Command to insert text into some kind of wrapper
    begin{center}
        MakeUppercase{task}
    end{center}
    vspace{4mm}
    @task   % Text declared using task command
    vspace{4mm}
    rule{4cm}{0.4pt}
}

main.tex – main tex file

documentclass[a4paper,oneside,12pt]{style}
begin{document}
task{input{to_include}}  % Including text from another tex file and defining as @task
typeTask  % Inserting wrapped defined text
end{document}

to_include.tex – latex text to include

Some text
begin{enumerate}
    item item 1
    item another item
        subitem and subitems
        subitem more subitems
    item latest item
end{enumerate}

I want to get the result corresponding to the LaTeX file:

documentclass[a4paper,oneside,12pt]{report}
begin{document}
    { % Header of wrapper from style.cls
        begin{center}
            MakeUppercase{task}
        end{center}
        vspace{4mm}
    }
    { % From include file
        Some text
        begin{enumerate}
            item item 1
            item another item
                subitem and subitems
                subitem more subitems
            item latest item
        end{enumerate}
    }
    { % Footer of wrapper from style.cls
        vspace{4mm}
        rule{4cm}{0.4pt}
    }
end{document}

instead of error. How to do this properly?

    vspace{4mm}
    @task   % Text declared using task command
    vspace{4mm}

    vspace{4mm}
    @task par  % Text declared using task command
    vspace{4mm}