\begin{table}
\centering
\begin{tblr}[         %% tabularray outer open
]                     %% tabularray outer close
{                     %% tabularray inner open
colspec={Q[]Q[]},
hline{2}={1-2}{solid, black, 0.05em},
hline{1}={1-2}{solid, black, 0.1em},
hline{4}={1-2}{solid, black, 0.1em},
}                     %% tabularray inner close
num & char \\
3.1 & 10\$ \\
3.14 & blah\_blah \\
\end{tblr}
\end{table} 
